1. An Electronic Primary Thermometer Based on Thermal Shot Noise
Lafe Spietz, K.W. Lehnert, Irfan Siddiqi,
R.J. Schoelkopf
Department Of Applied Physics, Yale University
Thanks to:
Michel Devoret and Dan Prober

2. Introduction
Thermal-shot noise in tunnel junctions: a voltage-dependent combination of Johnson noise and shot noise
Relates T and V using only e and kB
Demonstration of functional form for tunnel junction T=800 mK to >10 K

3. Fundamental Noise Sources
Johnson-Nyquist Noise
Frequency-independent
Temperature-dependent
Used for thermometry
Shot Noise
Frequency-independent
Temperature independent

4. Conduction in Tunnel Junctions
M I M
Difference gives current:
Assume: Tunneling amplitudes and
D.O.S. independent of Energy

5. Thermal-Shot Noise of a Tunnel Junction*
Sum gives noise:
*D. Rogovin and D.J. Scalpino, Ann Phys. 86,1 (1974)

6. Thermal-Shot Noise of a Tunnel Junction
2eI
Shot Noise
Transition Region
eV~kBT
4kBT
Johnson Noise R

7. Tunnel Junction: Dolan Bridge Fabrication
Dolan Resist Bridge(SEM)
Al-AlOX-Al Junction(AFM)

8. The Measurement
For t = 1 second

9. Self-Calibration Technique for Thermometry
P = GB( SIAmp+SI(V,T) )

10. Comparison of normalized data to functional form over wide range

11. Merits Vs. Complications
Fast and self-calibrating
Primary
Wide T range (mK to >10K)
No B-dependence
Measures electron temperature
Possibility to relate T to frequency!*
Complications
Self heating
Frequency dependence*
I(V) nonlinearities from:
Density of states
Barrier shape
Weak localization, etc
Amplifier nonlinearity
*R. J. Schoelkopf et al., Phys Rev. Lett. 80, 2437 (1998)

12. Summary
New Tunnel Junction Thermometer based on voltage and temperature dependent noise of a tunnel junction (thermal-shot noise.)
Fast, accurate thermometer
works over a wide temperature range
Relates T to V using only e and kb implications for metrology